Embedded magnet motor and manufacturing method of the same

ABSTRACT

In an embedded magnet motor, radial magnets and first inclined magnets form north poles. The radial magnets and second inclined magnets form south poles. Core sheets each include preformed radial accommodating slots the number of which is expressed by P/2. Some of the preformed radial accommodating slots are short slots and the rest are long slots. The short slots are located at some parts of each radial accommodating slot along the axial direction. Radially inner ends of the short slots restrict the radial magnets from moving radially inward.

CROSS REFERENCE TO RELATED APPLICATIONS

This divisional application claims the benefit under 35 U.S.C. §121 ofapplication Ser. No. 12/861,311 filed on Aug. 23, 2010 now U.S. Pat. No.7,868,503 which in turn claims the benefit under 35 U.S.C. §121 ofapplication Ser. No. 12/277,572 filed on Nov. 25, 2008 (now U.S. Pat.No. 7,800,272) and all of whose entire disclosures are incorporated byreference herein, and which in turn takes its priority from thefollowing Japanese applications: JP 2008-286866 filed Nov. 7, 2008; JP2008-170266 filed Jun. 30, 2008; JP 2008-108006 filed Apr. 17, 2008; JP2008-097195 filed Apr. 3, 2008; JP 2008-081412 filed Mar. 26, 2008; JP2007-307368; JP 2007-307369; and JP 2007-307370 all of which were filedNov. 28, 2007.

BACKGROUND OF THE INVENTION

The present invention relates to an embedded magnet motor and amanufacturing method of the same.

A rotor core of an embedded magnet motor disclosed in Japanese Laid-OpenPatent Publication No. 2007-195391 includes radial accommodating slotsthe number of which is expressed by P/2, first inclined accommodatingslots the number of which is expressed by P/2, and second inclinedaccommodating slots the number of which is expressed by P/2. The radialaccommodating slots extend in a substantially radial direction of therotor core as viewed from the axial direction. A pair of each firstinclined accommodating slot and the associated second inclinedaccommodating slot form a V-shaped accommodating slot. Each of theradial accommodating slots accommodates a radial magnet. Each of thefirst inclined accommodating slots accommodates a first inclined magnet.Each of the second inclined accommodating slots accommodates a secondinclined magnet. Each of the radial magnets and the adjacent firstinclined magnet form a north pole. Each of the radial magnets and theadjacent second inclined magnet form a south pole. As a result, northpoles the number of which is expressed by P/2 and south poles the numberof which is expressed by P/2 are formed.

Radially inner ends of the radial magnets of the above publication aresurrounded by walls of the radially inner ends of the radialaccommodating slots without any spaces.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide anew embedded magnet motor and a manufacturing method of the same.

One aspect of the present invention provides an embedded magnet motorincluding a rotor. An axis of the rotor is referred to as a rotor axis.The rotor includes a rotor core, radial magnets the number of which isexpressed by P/2, first inclined magnets the number of which isexpressed by P/2, and second inclined magnets the number of which isexpressed by P/2. The rotor core includes radial accommodating slots thenumber of which is expressed by P/2, first inclined accommodating slotsthe number of which is expressed by P/2, and second inclinedaccommodating slots the number of which is expressed by P/2. The radialaccommodating slots, the first inclined accommodating slots, and thesecond inclined accommodating slots extend entirely through the rotorcore in the axial direction. The radial accommodating slots extendsubstantially in a radial direction of the rotor core. The firstinclined accommodating slots and the second inclined accommodating slotsextend linearly to be inclined with respect to the radial accommodatingslots. A pair of each first inclined accommodating slot and theassociated second inclined accommodating slot form a V-shapedaccommodating slot. The V-shape points radially outward of the rotorcore. The radial accommodating slots and the V-shaped accommodatingslots being arranged alternately in the circumferential direction of therotor core. Each of the radial accommodating slots accommodates one ofthe radial magnets. Each of the first inclined accommodating slotsaccommodates one of the first inclined magnets. Each of the secondinclined accommodating slots accommodates one of the second inclinedmagnets. Each of the radial magnets is located between one of the firstinclined magnets and one of the second inclined magnets. Each radialmagnet and the circumferentially adjacent first inclined magnet form oneof a north pole and a south pole. Each radial magnet and thecircumferentially adjacent second inclined magnet form the other one ofthe north pole and the south pole. As a result, north poles the numberof which is expressed by P/2 and south poles the number of which isexpressed by P/2 are formed. That is, the number of magnetic poles ofthe rotor is expressed by P. The rotor core is formed by laminating aplurality of core sheets in the axial direction. Each core sheetincludes preformed radial accommodating slots the number of which isexpressed by P/2. The preformed radial accommodating slots aredistributed in the circumferential direction of the core sheet. Theradial accommodating slots are formed by laminating the preformed radialaccommodating slots. Some of the preformed radial accommodating slotsare short slots, and the rest are long slots. The distance between aradially inner end of each short slot and the rotor axis is referred toas a first radial distance R1. The distance between a radially inner endof each long slot and the rotor axis is referred to as a second radialdistance R2. Setting is performed to satisfy R2<R1. The short slots arelocated at some parts of each radial accommodating slot along the axialdirection. As a result, the radially inner ends of the short slotsrestrict the radial magnets from moving radially inward.

According to another aspect of the present invention, the radialdimension of the preformed radial accommodating slots is greater thanthe radial dimension of the radial magnets. Each core sheet includes aprojection, which projects at least in one of the preformed radialaccommodating slots. A direction perpendicular to the radial directionis referred to as a width direction. Each projection projects from onlyone of widthwise sides of the preformed radial accommodating slot. Theprojections are located at least at some parts of each radialaccommodating slot along the axial direction. As a result, theprojections restrict the radial magnets from moving radially inward.

According to another aspect of the present invention, each core sheetincludes preformed radial accommodating slots the number of which isexpressed by P/2, first preformed inclined accommodating slots thenumber of which is expressed by P/2, and second preformed inclinedaccommodating slots the number of which is expressed by P/2. Thepreformed radial accommodating slots are distributed in thecircumferential direction of the core sheet. The radial accommodatingslots are formed by laminating the preformed radial accommodating slots.The first inclined accommodating slots are formed by laminating thefirst preformed inclined accommodating slots. The second inclinedaccommodating slots are formed by laminating the second preformedinclined accommodating slots. Some of the preformed radial accommodatingslots in each core sheet are both-side communication slots, and the restare independent slots. The radially inner end of each both-sidecommunication slot communicates with both circumferentially adjacentfirst preformed inclined accommodating slot and the second preformedinclined accommodating slot. Each independent slot communicates neitherwith the first preformed inclined accommodating slot nor with the secondpreformed inclined accommodating slot. An inner bridge is providedbetween each independent slot and the associated first preformedinclined accommodating slot. Another inner bridge is provided betweeneach independent slot and the associated second preformed inclinedaccommodating slot. The independent slots are located at some parts ofeach radial accommodating slot along the axial direction. As a result,the inner bridges restrict the corresponding first inclined magnet andthe second inclined magnet from moving radially inward.

According to another aspect of the present invention, some of thepreformed radial accommodating slots at least in one of the core sheetsare one-side communication slots. Each of the one-side communicationslots communicates with one of the first preformed inclinedaccommodating slot and the second preformed inclined accommodating slot,and does not communicate with the other one. That is, an inner bridge isprovided between the other one of the first preformed inclinedaccommodating slot and the second preformed inclined accommodating slotand the one-side communication slot. The one-side communication slotsare located at least at some parts of each radial accommodating slotalong the axial direction.

According to another aspect of the present invention, some of thepreformed radial accommodating slots at least in one of the core sheetsare projecting communication slots. A radially inner end of eachprojecting communication slot communicates with the circumferentiallyadjacent first inclined accommodating slot and the second inclinedaccommodating slot. The radially inner end of the projectingcommunication slot is provided with a restricting projection, whichprojects radially outward. The projecting communication slots arelocated at least at some parts of each radial accommodating slot alongthe axial direction. As a result, the restricting projections restrictthe radial magnets from moving radially inward. The restrictingprojections restrict the first inclined magnets and the second inclinedmagnets from moving radially inward, thereby preventing the firstinclined magnets and the second inclined magnets from contacting theradial magnets.

According to another aspect of the present invention, a directionperpendicular to the direction in which each radial accommodating slotextends as viewed from the axial direction is referred to as a widthdirection. A wide slot is provided at a radially outer end of eachradial accommodating slot. A second width of the wide slots is greaterthan a first width of the radial magnets. Each of the radialaccommodating slot is provided with a projection formed radially inwardthan the associated wide slot. The width of part of the radialaccommodating slot constricted by the projection is less than the firstwidth of the radial magnet. As a result, the projections restrict theradial magnets from moving radially outward. The radial dimension of thewide slot is referred to as a wide radial dimension Y. The thickness ofeach core sheet is referred to as a core sheet thickness T. Setting isperformed to satisfy Y≦4T.

According to another aspect of the present invention, an outer bridge islocated between the radially outer end of each radial accommodating slotand an outer circumferential surface of the rotor core. The radialdimension of the outer bridge being referred to as AB. A V-slot outerbridge is provided between the radially outer end of each V-shapedaccommodating slot and the outer circumferential surface of the rotorcore. The radial dimension of the V-slot outer bridge is also AB. Abridge between inclined slots is provided between the radially outer endof each first inclined accommodating slot and the radially outer end ofthe associated second inclined accommodating slot. The width of thebridge between inclined slots is referred to as an inter-inclined slotbridge dimension BB. Setting is performed to satisfy BB>AB.

According to another aspect of the present invention, an inner bridge islocated between the radially inner end of each radial accommodating slotand the radially inner end of the associated first inclinedaccommodating slot. Another inner bridge is provided between theradially inner end of each radial accommodating slot and the radiallyinner end of the associated second inclined accommodating slot. Thewidth of the inner bridges is referred to as an inner bridge dimensionCB. A bridge between inclined slots is provided between the radiallyouter end of each first inclined accommodating slot and the radiallyouter end of the associated second inclined accommodating slot. Thewidth of the bridge between inclined slots is referred to as aninter-inclined slot bridge dimension BB. Setting is performed to satisfyBB>CB.

According to another aspect of the present invention, the embeddedmagnet motor includes a magnetic sensor. The magnetic sensor detectsrotation of the rotor by detecting axial magnetic flux leakage from therotor. The magnetic sensor is arranged in a radially outer region toface an axial end surface of the rotor. The magnetic sensor in theradially outer region detects the magnetic flux. Positive and negativepoles of the magnetic flux are reversed only once in one cycle ofmagnetic flux variation during a period when the rotor is rotated andthe magnetic sensor passes between the first inclined magnet and thesecond inclined magnet.

Another aspect of the present invention provides a manufacturing methodof an embedded magnet motor. The method includes: a step for arrangingthe magnetic sensor to face the axial end surface of the rotor; and ameasuring step for measuring magnetic characteristics detected by themagnetic sensor at every radial positions when the radial position ofthe magnetic sensor is changed. The method further includes apositioning step for determining the radially outer region based on theresult of the measuring step and determining the position of themagnetic sensor in the radially outer region.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a plan view illustrating an embedded magnet motor according toa first embodiment of the present invention;

FIG. 1A is an enlarged view illustrating an inner end of one of theradial accommodating slots of FIG. 1;

FIG. 2 is a plan view illustrating the core sheet of FIG. 1;

FIG. 3 is an enlarged perspective view illustrating the rotor core ofFIG. 1, and is a perspective view looking at a radially inner sectionfrom a radially outer section;

FIG. 4 is a characteristic diagram showing the relationship between theoverlap dimension R shown in FIG. 1A and the magnetizing rate of theradial magnets. The overlap dimension R is an overlapping amount of theopposing surface SX and the short slot;

FIG. 5 is a plan view illustrating an embedded magnet motor according toa second embodiment;

FIG. 6 is a plan view illustrating the core sheet of FIG. 5;

FIG. 7 is an enlarged perspective view illustrating the rotor core ofFIG. 5, and is a perspective view looking at a radially outer sectionfrom a radially inner section;

FIG. 8 is an enlarged perspective view opposite to FIG. 7, and is aperspective view looking at a radially inner section from a radiallyouter section;

FIG. 9 is a plan view illustrating a core sheet according to a thirdembodiment;

FIG. 10 is an enlarged perspective view illustrating the rotor coreformed by laminating core sheets of FIG. 9, and is a perspective viewlooking at a radially outer section from a radially inner section;

FIG. 11 is a plan view illustrating an embedded magnet motor accordingto a fourth embodiment;

FIG. 12 is a plan view illustrating the core sheet of FIG. 11;

FIG. 13 is an enlarged perspective view illustrating the rotor core ofFIG. 11, and is a perspective view looking at a radially inner sectionfrom a radially outer section;

FIG. 14 is a plan view illustrating an embedded magnet motor accordingto a fifth embodiment;

FIG. 15 is a plan view illustrating the core sheet of FIG. 14;

FIG. 16 is an enlarged perspective view illustrating the rotor core ofFIG. 14, and is a perspective view looking at a radially inner sectionfrom a radially outer section;

FIG. 17 is a plan view illustrating a core sheet according to a sixthembodiment;

FIG. 18 is a plan view illustrating an embedded magnet motor accordingto a seventh embodiment;

FIG. 19 is a plan view illustrating the core sheet of FIG. 18;

FIG. 20 is an enlarged perspective view illustrating the rotor core ofFIG. 18, and is a perspective view looking at a radially inner sectionfrom a radially outer section;

FIG. 21 is a plan view illustrating an embedded magnet motor accordingto an eighth embodiment;

FIG. 22 is a plan view illustrating the core sheet of FIG. 21;

FIG. 23 is a perspective view illustrating the rotor core of FIG. 21;

FIG. 23A is an enlarged perspective view illustrating a radially innerend of one of the radial accommodating slots of FIG. 23;

FIG. 24 is a plan view illustrating an embedded magnet motor accordingto a ninth embodiment;

FIG. 25 is a plan view illustrating the core sheet of FIG. 24;

FIG. 26 is a perspective view illustrating the rotor core of FIG. 24;

FIG. 26A is an enlarged perspective view illustrating a radially innerend of one of the radial accommodating slots of FIG. 26;

FIG. 27 is a plan view illustrating an embedded magnet motor accordingto a tenth embodiment;

FIG. 28 is a plan view illustrating the core sheet of FIG. 27;

FIG. 29 is a perspective view illustrating the rotor core of FIG. 27;

FIG. 29A is an enlarged perspective view illustrating a radially innerend of one of the radial accommodating slots of FIG. 29;

FIG. 30 is a plan view illustrating an embedded magnet motor accordingto an eleventh embodiment;

FIG. 31 is a plan view illustrating the core sheet of FIG. 30;

FIG. 32 is a perspective view illustrating the rotor core of FIG. 30;

FIG. 32A is an enlarged perspective view illustrating a radially innerend of one of the radial accommodating slots of FIG. 32;

FIG. 33 is a plan view illustrating an embedded magnet motor accordingto a twelfth embodiment;

FIG. 34 is a plan view illustrating the core sheet of FIG. 33;

FIG. 35 is a perspective view illustrating the rotor core of FIG. 33;

FIG. 35A is an enlarged perspective view illustrating a radially innerend of one of the radial accommodating slots of FIG. 35;

FIG. 36 is a plan view illustrating an embedded magnet motor accordingto a thirteenth embodiment;

FIG. 37 is a plan view illustrating the core sheet of FIG. 36;

FIG. 38 is a perspective view illustrating the rotor core of FIG. 36;

FIG. 38A is an enlarged perspective view illustrating a radially innerend of one of the radial accommodating slots of FIG. 38;

FIG. 39 is a plan view illustrating an embedded magnet motor accordingto a fourteenth embodiment;

FIG. 40A is a partial side view illustrating the laminated core sheetsof FIG. 39;

FIG. 40B is an enlarged plan view illustrating one of the wide slots ofFIG. 29;

FIG. 40C is an enlarged plan view illustrating a radially outer end ofone of the V-shaped accommodating slots of FIG. 29;

FIG. 40D is an enlarged plan view illustrating a radially inner end ofone of the V-shaped accommodating slots of FIG. 29;

FIG. 41 is a characteristic diagram between the radial dimension of thewide slots and the rotor size ratio;

FIG. 42 is a graph showing the rotor size ratio;

FIG. 43 is a cross-sectional view illustrating an embedded magnet motoraccording to a fifteenth embodiment;

FIG. 44 is a plan view illustrating the rotor and the stator of FIG. 43,and shows the inside of the yoke;

FIG. 45 is an enlarged plan view illustrating one of the V-shapedaccommodating slots of FIG. 44;

FIG. 46 is an enlarged plan view explaining a measuring step forselecting the position of the Hall IC in FIG. 45;

FIG. 47 is a characteristic diagram between rotational angle andmagnetic flux density showing characteristic lines Za to Zecorresponding to Hall ICs 51 a to 51 e of FIG. 46; and

FIG. 48 is a characteristic diagram between rotational angle andmagnetic flux density showing characteristic lines Zf to Zhcorresponding to Hall ICs 51 f to 51 h of FIG. 46.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 3 show a first embodiment of the present invention.

FIG. 1 shows an embedded magnet motor according to the first embodiment.The embedded magnet motor includes a stator 1 and a rotor 2. Theembedded magnet motor is an inner rotor motor. The axis of the rotor 2,that is, the central axis is referred to as a rotor axis 13.

The stator 1 is formed to be substantially cylindrical as a whole. Thestator 1 includes a stator core 5 and coils 6. The stator core 5includes a cylindrical portion 3 and teeth 4. The cylindrical portion 3forms the outer shape of the stator 1. The teeth 4, the number of whichis twelve, extend from the inner circumferential surface of thecylindrical portion 3 toward the rotor axis 13. The teeth 4 are locatedat equal angular intervals in the circumferential direction of thecylindrical portion 3. Each coil 6 is wound around one of the teeth 4via an insulator (not shown) by concentrated winding. FIG. 1 shows onlyone of the coils 6 with a chain double-dashed line.

The rotor 2 includes a rotating shaft 7, a rotor core 8, four radialmagnets 9, four first inclined magnets 71, and four second inclinedmagnets 72. The rotor core 8 is secured to the rotating shaft 7. Thenumber of the magnetic poles of the rotor 2 is expressed by P. In thefirst embodiment, the number of the magnetic poles P is set equal toeight. In the first embodiment, the diameter of the rotor 2, that is,the diameter of the rotor core 8 is set to 30 mm. The radial magnets 9,the first inclined magnets 71, and the second inclined magnets 72 aresubstantially rectangular solid.

FIG. 2 shows a core sheet 11. The rotor core 8 is formed to besubstantially cylindrical by laminating several core sheets 11 in theaxial direction as shown in FIG. 3. The core sheets 11 are laminatedwhile being displaced one at a time by 360/(P/2)° in the circumferentialdirection around the rotor axis 13. That is, in the first embodiment,the core sheets 11 are laminated while being rotated by 90° one at atime. Each core sheet 11 includes four fastening slots 18. Fasteningmembers, which are rivets 19 in the first embodiment, are insertedthrough the fastening slots 18 to secure the core sheets 11. Therotating shaft 7 is fitted in the central hole of the rotor core 8. As aresult, the rotor core 8 is rotatably supported inside the stator 1.

The rotor core 8 includes four radial accommodating slots 8 a, fourfirst inclined accommodating slots 81, and four second inclinedaccommodating slots 82. A pair of each first inclined accommodating slot81 and the associated second inclined accommodating slot 82 form aV-shaped accommodating slot 8 b. When the rotor core 8 is viewed fromthe axial direction, the V-shaped accommodating slots 8 b aresubstantially V-shaped pointing radially outward of the rotor core 8.Each pair of the first inclined accommodating slot 81 and the secondinclined accommodating slot 82 approach each other in a radially outwarddirection. That is, the rotor core 8 includes four V-shapedaccommodating slots 8 b. The first inclined accommodating slots 81 andthe second inclined accommodating slots 82 are straight lines inclinedin different directions with respect to the radial direction of therotor core 8. Each fastening slot 18 is located at the center of one ofthe V-shaped accommodating slots 8 b. That is, each fastening slot 18 islocated between one of the first inclined accommodating slots 81 and theassociated second inclined accommodating slot 82. Each first inclinedaccommodating slot 81 and the associated second inclined accommodatingslot 82 do not communicate with each other, and are independent fromeach other. In FIG. 1, each first inclined accommodating slot 81 islocated in the counterclockwise direction from the adjacent radialaccommodating slot 8 a. Each second inclined accommodating slot 82 islocated in the clockwise direction from the adjacent radialaccommodating slot 8 a.

The number of the radial accommodating slots 8 a and the V-shapedaccommodating slots 8 b are both P/2. Each radial accommodating slot 8 aand the V-shaped accommodating slot 8 b are formed at equal angularintervals alternately in the circumferential direction of the rotor core8. In the present embodiment, the radial accommodating slots 8 a arearranged at intervals of 90°, and the V-shaped accommodating slots 8 bare arranged at intervals of 90°.

The radial accommodating slots 8 a and the V-shaped accommodating slots8 b are accommodating slots extending entirely through the rotor core 8in the axial direction. The radial accommodating slots 8 a extend in theradial direction of the rotor core 8. Each of the radial accommodatingslots 8 a accommodates one of the radial magnets 9. Each of the firstinclined accommodating slots 81 accommodates one of the first inclinedmagnets 71. Each of the second inclined accommodating slots 82accommodates one of the second inclined magnets 72. Each of the radialmagnets 9 and the associated first inclined magnet 71 that are adjacentto each other form a north pole. Each of the radial magnets 9 and theassociated second inclined magnet 72 that are adjacent to each otherform a south pole. As a result, the rotor core 8 has four north polesand four south poles. The radial magnets 9, the first inclined magnets71, and the second inclined magnets 72 are magnetized after beingarranged in the radial accommodating slots 8 a and the V-shapedaccommodating slots 8 b to facilitate inserting them in the radialaccommodating slots 8 a and the V-shaped accommodating slots 8 b.

As shown in FIG. 1, a wide section, which is a wide slot 8 c in thefirst embodiment, is formed at the radially outer end of each radialaccommodating slot 8 a. When the rotor core 8 is viewed from the axialdirection, a direction perpendicular to the radial direction is referredto as a width direction. The width of the wide slots 8 c is set greaterthan the width of the radial magnets 9. That is, the width of the wideslots 8 c is greater than the width of part of the radial accommodatingslots 8 a other than the wide slots 8 c. The wide slots 8 c extendentirely through the rotor core 8 in the axial direction.

As shown in FIG. 1, the rotor core 8 includes outer circumferentialprojections 8 d formed at the radially outer end of each radialaccommodating slot 8 a. A pair of the outer circumferential projections8 d project from both circumferential sides of each radial accommodatingslot 8 a toward the inside of the radial accommodating slot 8 a by thesame amount in the circumferential direction. Each pair of outercircumferential projections 8 d do not contact each other. The outercircumferential projections 8 d are located radially inward than thewide slots 8 c. That is, the portion between each radial accommodatingslot 8 a and the associated wide slot 8 c is constricted by the outercircumferential projections 8 d. The width between the pair of outercircumferential projections 8 d is less than the width of the radialaccommodating slots 8 a and the width of the wide slots 8 c. The outercircumferential projections 8 d serve as outer projections that restrictthe radial magnets 9 from moving radially outward. That is, the outercircumferential projections 8 d prevent displacement of the radialmagnets 9.

As shown in FIG. 3, the outer circumferential projections 8 d arelocated at some parts of each radial accommodating slot 8 a along theaxial direction. In the present embodiment, the number of the coresheets 11 arranged between axially adjacent outer circumferentialprojections 8 d is three.

As shown in FIG. 1, the rotor core 8 includes inner restricting portions8 e formed at the radially inner ends of the radial accommodating slots8 a. The inner restricting portions 8 e are inner projections, whichproject radially outward from the radially inner ends of the radialaccommodating slots 8 a to the inside of the radial accommodating slots8 a. The width of the inner restricting portions 8 e is the same as thewidth of the radial accommodating slots 8 a. The inner restrictingportions 8 e restrict the radial magnets 9 from moving radially inward.

As shown in FIG. 3, the inner restricting portions 8 e are located atsome parts of each radial accommodating slot 8 a along the axialdirection. In the present embodiment, the number of the core sheets 11arranged between axially adjacent inner restricting portions 8 e isthree.

As shown in FIG. 1, V-slot outer gaps 8 g, in which the first inclinedmagnet 71 and the second inclined magnet 72 are not arranged, areprovided at the radially outer ends of the first inclined accommodatingslot 81 and the second inclined accommodating slot 82. The width of theV-slot outer gaps 8 g is substantially the same as the width of thefirst inclined magnets 71 and the second inclined magnets 72. The rotorcore 8 has V-slot projections 8 h located at the radially outer ends ofthe first inclined accommodating slots 81 and the second inclinedaccommodating slots 82. The V-slot projections 8 h are located radiallyinward than the V-slot outer gaps 8 g. The V-slot projections 8 hproject toward the inside of the first inclined accommodating slots 81and the second inclined accommodating slots 82 in the circumferentialdirection. That is, the portion between each first inclined magnet 71and the associated V-slot outer gap 8 g is constricted by one of theV-slot projections 8 h. The portion between each second inclined magnet72 and the associated V-slot outer gap 8 g is also restricted by anotherV-slot projection 8 h. The V-slot projections 8 h restrict the firstinclined magnets 71 and the second inclined magnets 72 from movingradially outward, that is, toward the V-slot outer gaps 8 g. A pair ofthe V-slot projections 8 h project in the opposite directions along thecircumferential direction by the same amount.

As shown in FIG. 1A, each radial accommodating slot 8 a is defined by apair of radial accommodating slot side surfaces 8 p, which extendsubstantially in the radial direction. The radially inner ends of thefirst inclined accommodating slots and the second inclined accommodatingslots 82 have opposing surfaces SX. The opposing surfaces SX face theradial accommodating slot side surfaces 8 p, and extend substantiallyparallel to the radial accommodating slot side surfaces 8 p. An innerbridge 8 i is located between each opposing surface SX and theassociated radial accommodating slot 8 a. The width of the inner bridges8 i is constant along the radial direction. A triangular gap 8 j isprovided at the radially inner end of each of the first inclinedaccommodating slots 81 and the second inclined accommodating slots 82.The triangular gaps 8 j are substantially triangular extended portionsas viewed from the axial direction. As a result, the opposing surfacesSX are formed.

As shown in FIG. 1, the rotor core 8 has wide outer bridges 8 k thenumber of which is expressed by P/2, V-slot outer bridges 8 w the numberof which is expressed by P, and inter-inclined slot bridges 8 m thenumber of which is expressed by P/2. The wide outer bridges 8 k arebridge portions each located between one of the wide slots 8 c and arotor outer circumferential surface 8 r. The rotor outer circumferentialsurface 8 r is an outer circumferential surface of the rotor core 8. TheV-slot outer bridges 8 w are bridge portions located between the V-slotouter gaps 8 g and the rotor outer circumferential surface 8 r. Theinter-inclined slot bridges 8 m are bridge portions each located betweenthe radially outer end of one of the first inclined accommodating slots81 and the radially outer end of the associated second inclinedaccommodating slot 82, and connected to a pair of the V-slot outerbridges 8 w.

As shown in FIG. 2, each of the core sheets 11 includes a short slot 11a and three long slots 11 b. That is, in each of the core sheets 11, thenumber of the long slots 11 b is obtained by subtracting the number ofthe short slot 11 a from P/2. The short slot 11 a and the long slots 11b form the radial accommodating slots 8 a when several core sheets 11are laminated. That is, the short slot 11 a and the long slots 11 b arepreformed lamination radial accommodating slots, which are preformedradial accommodating slots in the first embodiment. In other words, thecore sheets 11 have the preformed radial accommodating slots the numberof which is expressed by P/2.

Furthermore, each of the core sheets 11 has four first preformedinclined accommodating slots 61 and four second preformed inclinedaccommodating slots 62. The first inclined accommodating slots 81 areformed by laminating the first preformed inclined accommodating slots61. The second inclined accommodating slots 82 are formed by laminatingthe second preformed inclined accommodating slots 62. A pair of eachfirst preformed inclined accommodating slot 61 and the associated secondpreformed inclined accommodating slot 62 form a preformed V-shapedaccommodating slot. That is, each of the core sheets 11 has thepreformed V-shaped accommodating slots the number of which is expressedby P/2, that is four. The preformed V-shaped accommodating slots arepreformed lamination V-shaped accommodating slots, which form theV-shaped accommodating slots 8 b when laminated.

Each of the core sheets 11 is divided into an inner ring 11 s and anouter ring 11 t. The inner ring 11 s is located radially inward of theshort slot 11 a, the long slots 11 b, the first preformed inclinedaccommodating slots 61, and the second preformed inclined accommodatingslots 62. The outer ring lit is located radially outward of the same.The inner bridges 8 i and the inter-inclined slot bridges 8 m connectthe inner ring 11 s to the outer ring 11 t. The inner ring 11 s and theouter ring 11 t occupy large part of each core sheet 11.

The radially inner end of the short slot 11 a forms the innerrestricting portion 8 e. The long slots 11 b extend radially inward thanthe short slot 11 a. As shown in FIG. 2, the distance between theradially inner end of the short slot 11 a and the rotor axis 13 isreferred to as a first radial distance R1. The distance between theradially inner end of each long slot 11 b and the rotor axis 13 isreferred to as a second radial distance R2. The distance between theradially inner end of each first inclined accommodating slot 81 and therotor axis 13 is referred to as a third radial distance R3. In thepresent embodiment, the third radial distance R3 is equal to thedistance between the radially inner end of each second inclinedaccommodating slot 82 and the rotor axis 13.

The first radial distance R1 is greater than the second radial distanceR2 (R2<R1). In the present embodiment, the first radial distance R1 isset greater than the third radial distance R3 (R3<R1). The second radialdistance R2 is set less than or equal to the third radial distance R3(R2≦R3). In the present embodiment, the second radial distance R2 is setsubstantially equal to the third radial distance R3.

In the first embodiment, the outer circumferential projections 8 d areprovided in only the short slot 11 a of each core sheet 11.

As shown in FIG. 1A, the dimension of the opposing surfaces SX along theradial accommodating slot side surfaces 8 p is referred to as anopposing surface dimension SW. The dimension of part of each opposingsurface SX corresponding to the short slot 11 a is referred to as anoverlap dimension R. The overlap dimension R is set to satisfy 0<R≦SW/2.In the present embodiment, the overlap dimension R is set equal to SW/2.In the present embodiment, the opposing surface dimension SW is equal to2 mm, and the overlap dimension R is equal to 1 mm.

The first embodiment has the following advantages.

(1) As shown in FIGS. 1 and 3, the short slots 11 a, that is, the innerrestricting portions 8 e are arranged at some parts of each radialaccommodating slot 8 a along the axial direction. The inner restrictingportions 8 e restrict the radial magnets 9 from moving radially inward.Portions of each radial accommodating slot 8 a where the long slots 11 bare provided form gaps with respect to the associated radial magnet 9.Thus, the magnetic resistance is increased. That is, the long slots 11 bseparate the magnetic paths from the radial magnet 9. As a result,magnetic flux leakage of the embedded magnet motor is reduced. Thus, theeffective magnetic flux of the embedded magnet motor is maintained andthe torque is easily increased.

For example, in the publication mentioned in BACKGROUND ART, theradially inner ends of the radial magnets are surrounded by the radiallyinner walls of the radial accommodating slots without any spaces. As aresult, parts of the rotor core that form the radially inner ends of theradial accommodating slots configure magnetic paths having smallmagnetic resistance, which might cause magnetic flux leakage. Thepresent embodiment solves such a problem.

The short slot 11 a and the long slots 11 b are formed by punching eachcore sheet 11. For restricting the radial magnets 9 from moving radiallyinward, for example, projections such as the outer circumferentialprojections 8 d may be provided at the radially inner ends of the radialaccommodating slots 8 a. However, the short slot 11 a and the long slots11 b according to the present embodiment are easily manufactured.

(2) As shown in FIG. 2, each core sheet 11 has only one short slot 11 a.The short slot 11 a undesirably reduces the magnetic resistance of thecore sheet 11. The present embodiment reduces the magnetic flux leakageas compared to a case where each core sheet 11 has several short slots11 a. That is, the magnetic resistance of the rotor core 8 is maximizedas a whole.

(3) As shown in FIG. 2, the second radial distance R2 is set less thanor equal to the third radial distance R3 (R2≦R 3). That is, the distancebetween the radially inner end of the long slots 11 b and the rotor axis13 is set less than or equal to the distance between the rotor axis 13and the radially inner end of the first inclined accommodating slots 81.Therefore, the inner bridges 8 i, which serve as the magnetic paths,become narrow at least at the portion defined by the long slots 11 b.Thus, the magnetic flux leakage is reliably reduced.

(4) As shown in FIG. 2, the first radial distance R1 is set greater thanthe third radial distance R3 (R3<R1). That is, the distance between theradially inner end of the short slot 11 a, that is, the radially innerend of the radial magnet and the rotor axis 13 is set greater than thedistance between the rotor axis 13 and the radially inner end of thefirst inclined accommodating slots 81. The following advantages areobtained by magnetizing the radial magnets 9 after the first inclinedmagnets 71 and the second inclined magnets 72. That is, magneticmaterial accommodated in the radial accommodating slots 8 a is easilyand reliably magnetized while suppressing them from being affected bythe first inclined magnets 71 and the second inclined magnets 72. Thus,inefficiency of the radial magnets 9 is reduced. This advantage wasconfirmed by the following experiment. That is, when the first radialdistance R1 was substantially equal to the third radial distance R3, theradially inner ends of the radial magnets 9 were poorly magnetized, thatis, there were inefficiency caused in the magnets when the radialmagnets 9 were magnetized after the first inclined magnets 71 and thesecond inclined magnets 72 were magnetized. To solve this problem, R3 isset smaller than R1 (R3<R1).

(5) As shown in FIG. 1A, the opposing surfaces SX are provided at theradially inner ends of the first inclined accommodating slots 81 and thesecond inclined accommodating slots 82. Thus, the width of each innerbridge 8 i is constant along the radial direction. Therefore, the widthof the inner bridges 8 i, or the magnetic paths, is made evenly narrowalong the radial direction, which further reduces the magnetic fluxleakage.

(6) FIG. 4 shows the experimental result of the relationship between theratio of the overlap dimension R to the opposing surface dimension SWand the magnetizing rate of the radially inner ends of the radialmagnets 9. The magnetizing rate is reduced in the order of R=0, R=SW/4,R=SW/2, R=3SW/4, and R=SW. That is, the magnetizing rate is reduced whenthe overlap ratio R/SW is increased. When 0<R≦SW/2, the magnetizing rateis greater than a case when SW/2<R≦SW. Thus, in the first embodiment, tosatisfy 0<R≦SW/2, R is set equal to SW/2 (R=SW/2). Therefore, a suitablemagnetizing rate is obtained, and inefficiency of the radial magnets 9is reduced in a suitable manner.

(7) The core sheets 11 as shown in FIG. 2 are laminated while beingdisplaced one at a time by 360/(P/2)° in the circumferential direction.In the present embodiment, the core sheets 11 are laminated while beingrotated by 90° each to form the rotor core 8. Thus, the operation ofrotating and laminating the core sheets 11 is constant, whichfacilitates the manufacture. That is, the laminating process of the coresheets 11 is easily automated.

As shown in FIG. 3, by laminating the core sheets 11 while displacingthem by a certain angle, the short slots 11 a, that is, the innerrestricting portions 8 e are arranged at regular intervals in eachradial accommodating slot 8 a along the axial direction. In the presentembodiment, three core sheets 11 are arranged between axially adjacentinner restricting portions 8 e. Therefore, the inner restrictingportions 8 e are provided regularly along the axial direction. The innerrestricting portions 8 e support the radial magnets 9 in a balancedmanner. This is because the inner restricting portions 8 e arranged atequal intervals along the axial direction evenly restrict the radialmagnets 9 from moving radially inward at regular intervals in the axialdirection.

FIGS. 5 to 8 show an embedded magnet motor according to a secondembodiment of the present invention.

As shown in FIG. 5, the rotor core 8 of the second embodiment includesinward projections 8 n the number of which is expressed by P/2 insteadof the outer circumferential projections 8 d. The inward projections 8 nproject radially inward from the radially outer ends of the radialaccommodating slots 8 a. The width of the radial magnets 9 is referredto as a first width W1. The width of the wide slots 8 c is referred toas a second width W2. The width of the inward projections 8 n isreferred to as a third width W3.

In this case, W3<W1<W2 is satisfied.

That is, the width of the inward projections 8 n is smaller than thewidth of the radial magnets 9. Each inward projection 8 n is located atthe middle of one of the wide slots 8 c in the circumferentialdirection. The inward projections 8 n restrict the radial magnets 9 frommoving radially outward.

As shown in FIG. 6, the core sheets 11 of the present embodiment includethe inward projections 8 n only in the short slots 11 a. The core sheets11 of FIG. 6 are laminated around the rotor axis 13 while being rotatedone at a time by 360/(P/2)°, that is, by 90°. As a result, the rotorcore 8 is manufactured. The radial dimension of the radial magnets 9 ofFIG. 5 may be greater than the radial dimension of the radial magnets 9of FIG. 1. This is because the outer circumferential projections 8 d arenot provided in FIG. 5.

A dimension obtained by subtracting the radial dimension of part of theradial magnet 9 facing the inner bridge 8 i from the radial dimension ofthe radial magnet 9 is referred to as an exposed dimension of the radialmagnet 9. That is, the exposed dimension of the radial magnet 9represents the dimension of part of magnetic flux input and outputsurfaces of the radial magnet 9 facing magnetic flux input and outputsurfaces of the first inclined magnet 71 and the second inclined magnet72. The magnetic flux input and output surfaces of the radial magnet 9are surfaces that contact the radial accommodating slot side surfaces 8p. The magnetic flux input and output surfaces of each first inclinedmagnet 71 are surfaces extending along the first inclined magnet 71. Inthe case of FIG. 5, the exposed dimension of the radial magnets 9 is setto 4.75 mm. In the case of FIG. 1, if the radial dimension of the outercircumferential projections 8 d is set to 0.5 mm, the exposed dimensionof the radial magnets 9 is 4.25 mm. That is, the exposed dimension ofthe radial magnets 9 of FIG. 1 is smaller than the exposed dimension ofthe radial magnets 9 of FIG. 5 by the amount corresponding to the radialdimension of the outer circumferential projections 8 d.

As a result, according to the result of experiments conducted using thesame amount of current, the applied torque of the embedded magnet motorof FIG. 5 was higher than the applied torque of the embedded magnetmotor of FIG. 1 by 4%. Also, the cogging torque of the embedded magnetmotor of FIG. 5 was lower than the cogging torque of the embedded magnetmotor of FIG. 1 by 27%. Further, the torque ripple of the embeddedmagnet motor of FIG. 5 was lower than the torque ripple of the embeddedmagnet motor of FIG. 1 by 7%.

The second embodiment has the following advantages.

(8) Each of the inward projections 8 n is located at the middle of oneof the wide slots 8 c in the circumferential direction. The radialdimension of the inward projections 8 n is set equal to the radialdimension of the wide slots 8 c. Thus, the radial position of the distalend of each inward projection 8 n matches the radial position of theradially inner end of the associated wide slot 8 c. For example, sincethe outer circumferential projections 8 d of FIG. 1 project in theradial accommodating slots 8 a, the outer circumferential projections 8d obstruct the radial magnets 9 from extending close to the wide slots 8c. However, since the inward projections 8 n of FIG. 5 are provided onlyin the wide slots 8 c, the radial magnets 9 are allowed to extend closeto the wide slots 8 c. Thus, the efficiency of the embedded magnet motorof FIG. 5 is improved easily as compared to the embedded magnet motor ofFIG. 1.

(9) As shown in FIG. 7, the width of the inward projections 8 n of thepresent embodiment is set to approximately ⅓ of the width of the radialmagnets 9. That is, the width of the inward projections 8 n is set toless than or equal to ½ the width of the radial magnets 9. For example,the pair of outer circumferential projections 8 d of FIG. 1 reduce thewidth of the associated radial accommodating slot 8 a. That is, theouter circumferential projections 8 d form a narrow portion in theassociated radial accommodating slot 8 a, which may cause magnetic fluxleakage. This is because although the pair of outer circumferentialprojections 8 d are separate from each other, the outer circumferentialprojections 8 d extend from the radial accommodating slot side surfaces8 p, and therefore reduces the gap between the radial accommodating slotside surfaces 8 p.

However, the width of the inward projections 8 n of FIG. 5 is set suchthat the inward projections 8 n are separate from the radialaccommodating slot side surfaces 8 p, and is set smaller than the widthof the radial magnets 9. Thus, the inward projections 8 n of FIG. 5 donot easily form a magnetic path of magnetic flux leakage, and readilyreduce the magnetic flux leakage. Thus, the embedded magnet motor ofFIG. 5 easily increases the efficiency as compared to the embeddedmagnet motor of FIG. 1.

(10) The inward projections 8 n are formed at some parts of each radialaccommodating slot 8 a along the axial direction. That is, the inwardprojections 8 n are formed at some parts of the rotor core 8 along theaxial direction. The number of the core sheets 11 arranged betweenaxially adjacent inward projections 8 n is three. Thus, for example, ascompared to a case where the inward projections 8 n extend entirelyalong the axial direction, the magnetic resistance of the entire radialaccommodating slots 8 a is increased. Thus, the magnetic flux leakage isfurther reduced. That is, the inward projections 8 n are suppressed fromundesirably reducing the magnetic resistance.

(11) As shown in FIG. 6, each of the core sheets 11 includes the shortslot 11 a provided with the inward projection 8 n, and the long slots 11b, which do not have the inward projections 8 n. By laminating such coresheets 11, the rotor core 8 is easily manufactured such that the inwardprojections 8 n are located only at some parts of the rotor core 8 alongthe axial direction.

(12) The inward projection 8 n is located only in the short slot 11 a ofeach core sheet 11. That is, the inner restricting portion 8 e and theinward projection 8 n are both provided in the short slot 11 a of eachcore sheet 11. Thus, the inner restricting portions 8 e and the inwardprojections 8 n are both located at the same axial positions in eachradial accommodating slot 8 a. Thus, each radial magnet 9 is restrictedfrom moving radially outward and radially inward at the same axialposition. Thus, the radial magnets 9 are retained in a balanced manner.

FIGS. 9 and 10 show a third embodiment.

The rotor core 8 of FIG. 10 may be formed by laminating the core sheets12 of FIG. 9 and the core sheets 11 of FIG. 6. That is, the embodimentis not limited to laminating only one type of the core sheets 11. Thecore sheet 12 of FIG. 9 does not have the short slot 11 a, and thepreformed radial accommodating slots the number of which is expressed byP/2 are all long slots 11 b. The inward projections 8 n are located atsome parts of each radial accommodating slot 8 a along the axialdirection. The number of the core sheets 11 located between axiallyadjacent inward projections 8 n is seven. The core sheets 11 of FIG. 6are laminated while being rotated by 90° each. The number and amount ofthe inner restricting portions 8 e and the inward projections 8 nprovided along the axial direction of the rotor core 8 of FIG. 10 areless than those of the rotor core 8 of FIG. 1 or FIG. 5. Thus, the rotorcore 8 of FIG. 10 further increases the magnetic resistance, and furtherreduces the magnetic flux leakage.

FIGS. 11 to 13 show a fourth embodiment of the present invention.

As shown in FIG. 13, the wide slots 8 c and the pairs of outercircumferential projections 8 d are located at the radially outer end ofeach radial accommodating slot 8 a. The number of the core sheets 11located between axially adjacent outer circumferential projections 8 dis three.

As shown in FIG. 11, the rotor core 8 includes inner circumferentialprojections 8 u in each radial accommodating slot 8 a. The innercircumferential projections 8 u are slightly separated from the radiallyinner end of each radial accommodating slot 8 a. In the presentembodiment, the projection amount of each inner circumferentialprojection 8 u from the associated radial accommodating slot sidesurface 8 p is set greater than half the width of the radialaccommodating slot 8 a. As a result, the inner circumferentialprojections 8 u restrict the radial magnets 9 from moving radiallyinward.

The inner circumferential projections 8 u are provided only on one ofthe pair of radial accommodating slot side surfaces 8 p. In the case ofFIG. 11, the inner circumferential projections 8 u project in thecircumferential direction only from the radial accommodating slot sidesurface 8 p in the counterclockwise direction to be located in theradial accommodating slots 8 a. The inner circumferential projections 8u are located at some parts of the radial accommodating slots 8 a alongthe axial direction. As shown in FIG. 13, the number of the core sheets11 provided between axially adjacent inner circumferential projections 8u is three.

As shown in FIG. 12, each core sheet 11 has the long slots 11 b thenumber of which is expressed by P/2, that is, four. The radial dimensionof the long slots 11 b is greater than the radial dimension of theradial magnets 9. In the present embodiment, each core sheet 11 has theinner circumferential projection 8 u and the pair of outercircumferential projections 8 d only in one of the long slots 11 b. Thatis, in the present embodiment, the inner circumferential projection 8 uand the outer circumferential projections 8 d are not formed in three ofthe long slots 11 b of each core sheet 11. The distance between therotor axis 13 and the inner circumferential projection 8 u is referredto as the first radial distance R1.

The fourth embodiment has the following advantages.

(13) As shown in FIG. 13, the inner circumferential projections 8 u arelocated at some parts of each radial accommodating slot 8 a along theaxial direction. The inner circumferential projections 8 u restrict theradial magnets 9 from moving radially inward. The radial dimension ofthe radial accommodating slots 8 a is greater than the radial dimensionof the radial magnets 9. The radially inner ends of the radialaccommodating slots 8 a are separate from the radial magnets 9 since theinner circumferential projections 8 u are provided. That is, themagnetic path is separate from the radial magnets 9. Thus, the magneticresistance at the radially inner ends of the radial accommodating slots8 a is increased, and thus the magnetic flux leakage is reduced.

As shown in FIGS. 11 and 13, the inner circumferential projections 8 uare located on only one of the pair of radial accommodating slot sidesurfaces 8 p. Thus, for example, as compared to a case where the innercircumferential projections 8 u are located on both of the pair ofradial accommodating slot side surfaces 8 p, punching of the core sheets11 of FIGS. 11 to 13 is easy, which facilitates the manufacture.

(14) As shown in FIG. 12, each core sheet 11 includes only one innercircumferential projection 8 u. Thus, for example, as compared to a casewhere each core sheet 11 includes several inner circumferentialprojections 8 u, the magnetic resistance of the entire rotor core 8 isincreased, and the magnetic flux leakage is reduced.

(15) The second radial distance R2 is set less than or equal to thethird radial distance R3. In the present embodiment, the second radialdistance R2 is set slightly less than the third radial distance R3.Thus, the magnetic paths, which are the inner bridges 8 i in the fourthembodiment, are narrowed, and the magnetic flux leakage is reduced.

(16) The first radial distance R1 is set greater than the third radialdistance R3 (R3<R1). Therefore, when magnetizing the radial magnets 9after the first inclined magnets 71 and the second inclined magnets 72,the radial magnets 9 are not easily affected by the first inclinedmagnets 71 and the second inclined magnets 72, and are easily andreliably magnetized. Thus, the inefficiency of the radial magnets 9 isreduced.

(17) The core sheets 11 shown in FIG. 12 are laminated while beingdisplaced one at a time by 360/(P/2)°, that is, by 90° in thecircumferential direction. Therefore, the operation of rotating andlaminating the core sheets 11 is constant, which facilitates automation.Also, since the inner circumferential projections 8 u are provided atregular intervals in the axial direction, the radial magnets 9 aresupported in a balanced manner.

FIGS. 14 to 16 show a fifth embodiment of the present invention.

FIG. 14 shows a rotor core 21 according to the fifth embodiment. Asshown in FIGS. 14 and 16, inner radial projections 22 b are provided onboth of the pair of radial accommodating slot side surfaces 8 p ofradial accommodating slots 21 a.

As shown in FIG. 15, each core sheet 22 includes the long slots 11 b thenumber of which is expressed by P/2. All the long slots 11 b areprovided with one of the inner radial projections 22 b. The inner radialprojection 22 b is located on only one of the circumferential sides ofeach long slot 11 b. In FIG. 15, the inner radial projection 22 b islocated on only the counterclockwise side surface. The pair of outercircumferential projections 8 d are formed in all the long slots 11 b.

The core sheets 22 of FIG. 15 are laminated with each core sheet 22being turned over the preceding core sheet 22 to form the rotor core 21of FIG. 14. As shown in FIG. 16, the inner radial projections 22 b arearranged in a staggered pattern along the axial direction.

The fifth embodiment has the following advantages.

(18) The inner radial projections 22 b project from the alternate radialaccommodating slot side surfaces 8 p per each core sheet 11. Thus, theinner radial projections 22 b of FIG. 16 support the radial magnets 9 ina more balanced manner as compared to the inner circumferentialprojections 8 u of FIG. 13.

(19) The same number of the inner radial projections 22 b are arrangedon each of the pair of radial accommodating slot side surfaces 8 p.Thus, the balance of the rotor core 21 such as the rotation balance issatisfactory. This reduces vibration caused by imbalance of the rotorcore 21.

(20) The projection amount of the inner radial projections 22 b is setless than half the width of the radial accommodating slots 21 a. Thus,the inner radial projections 22 b are prevented from contacting eachother. That is, the magnetic resistance of the rotor core 21 issuppressed from being reduced. In other words, the magnetic path issuppressed from being shortened.

FIG. 17 shows a core sheet 31 according to a sixth embodiment.

The core sheet 31 includes inner radial projections 31 a the number ofwhich is P/2. Each inner radial projection 31 a bulges radially outwardfrom one of the widthwise corners of the radially inner end of one ofthe long slots 11 b. That is, the inner radial projections 31 a are notseparate from the radially inner ends of the radial accommodating slots8 a. The width of the long slots 11 b is reduced toward the radiallyinner end. In each core sheet 31, the inner radial projections 31 a arearranged in all the four long slots 11 b. The rotor core is formed bylaminating several core sheets 31 without rotating them. The rigidity ofthe inner radial projections 31 a of FIG. 17 is greater than therigidity of the inner circumferential projections 8 u of FIG. 13 and therigidity of the inner radial projections 22 b of FIG. 16. Thus, theinner radial projections 31 a of FIG. 17 are not easily deformed, andthe radial magnets 9 are strongly restricted from moving radiallyinward. To increase the length of the magnetic path, the embodimentsillustrated in FIGS. 13 and 16 are preferred than the embodiment of FIG.17.

FIGS. 18 to 20 show a seventh embodiment of the present invention.

The wide slots 8 c extend through the rotor core 8 entirely in the axialdirection. The pair of outer circumferential projections 8 d arearranged between each wide slot 8 c and the radially outer end of theassociated radial accommodating slot 8 a. The outer circumferentialprojections 8 d are provided over the entire axial direction of therotor core 8. The projecting amounts of the outer circumferentialprojections 8 d are the same.

As shown in FIG. 20, the inner bridges 8 i of the present embodiment arelocated at some parts along the axial direction. The number of the coresheets 11 provided between axially adjacent inner bridges 8 i is three.

As shown in FIG. 19, each of the core sheets 11 includes one independentslot 11 c and three both-side communication slots 11 d. The independentslot 11 c and the both-side communication slots 11 d are the preformedradial accommodating slots the number of which is four, that is, P/2.The radially inner end of each both-side communication slot 11 dcommunicates with the circumferentially adjacent first preformedinclined accommodating slot 61 and the second preformed inclinedaccommodating slot 62. The independent slot 11 c communicate neitherwith the first preformed inclined accommodating slot 61 nor with thesecond preformed inclined accommodating slot 62. That is, the innerbridge 8 i is provided between the independent slot 11 c and the firstpreformed inclined accommodating slot 61. The inner bridge 8 i is alsoprovided between the independent slot 11 c and the second preformedinclined accommodating slot 62.

The seventh embodiment has the following advantages.

(21) The independent slot 11 c is located at some parts of each radialaccommodating slot 8 a along the axial direction. As a result, the innerbridges 8 i restrict the first inclined magnets 71 and the secondinclined magnets 72 from moving radially inward. As a result, the firstinclined magnets 71 and the second inclined magnets 72 are restrictedfrom moving radially inward at some parts of the rotor core 8 along theaxial direction. That is, gaps are provided between some parts of eachradial accommodating slot 8 a corresponding to the both-sidecommunication slots 11 d and the inner end of the associated firstinclined magnet 71 since the inner bridges 8 i are not provided. Gapsare also provided between some parts of each radial accommodating slot 8a corresponding to the both-side communication slots 11 d and theradially inner end of the associated second inclined magnet 72. Thus,the magnetic resistance is increased at the radially inner ends of thefirst inclined magnets 71 and the second inclined magnets 72, and themagnetic flux leakage is reduced.

The both-side communication slots 11 d and the independent slot 11 c areeasily manufactured by punching each core sheet 11. The punching of theboth-side communication slots 11 d and the independent slot 11 c iseasier than, for example, forming projections such as the innerrestricting portions 8 e of FIG. 1. The inner bridges 8 i connect theinner ring 11 s of each core sheet 11 to the outer ring lit in theradial direction. Thus, the inner bridges 8 i have high strengthalthough the inner bridges 8 i are thin in the direction of restrictingthe movement of the first inclined magnets 71 and the second inclinedmagnets 72, as compared to, for example, the inner restricting portions8 e of FIG. 1. The length of the first inclined magnets 71 and thesecond inclined magnets 72 can be increased by the amount correspondingto the thickness of the inner bridges 8 i that can be reduced.

(22) The number of the independent slot 11 c formed on each core sheet11 is one. The independent slot 11 c undesirably reduces the magneticresistance of the rotor core 8 as compared to the both-sidecommunication slots 11 d. However, since each core sheet 11 is providedwith one independent slot 11 c in the present embodiment, the magneticresistance of the entire rotor core 8 is increased, and the magneticflux leakage is minimized.

(23) The core sheets 11 are laminated along the rotor axis 13 whilebeing rotated one at a time by 360/(P/2)°, that is, by 90°. Since therotating and laminating operation of the core sheets 11 are constant,the rotor core 8 is easily manufactured, and automation is easy. Theindependent slot 11 c and the inner bridges 8 i are provided along therotor axis at regular intervals. In the present embodiment, three coresheets 11 are located between axially adjacent independent slots 11 c.Thus, the inner bridges 8 i restrict the radially inward movement of thefirst inclined magnets 71 and the second inclined magnets 72 evenlyalong the axial direction. Thus, the first inclined magnets 71 and thesecond inclined magnets 72 are supported in a balanced manner.

(24) The width of the inner bridges 8 i is constant along the radialdirection as viewed from the axial direction. Thus, the width of theinner bridges 8 i is evenly reduced, thereby reducing the magnetic fluxleakage.

(25) Each of the first inclined accommodating slots 81 and theassociated second inclined accommodating slot 82 do not communicate witheach other. That is, the inter-inclined slot bridges 8 m extending inthe radial direction is formed between each first inclined accommodatingslot 81 and the associated second inclined accommodating slot 82. Thewide outer bridges 8 k are connected to the inter-inclined slot bridges8 m. Thus, the strength is increased and deformation is prevented in therotor core 8 of the present embodiment as compared to a case where, forexample, each first inclined accommodating slot 81 communicates with theassociated second inclined accommodating slots 82.

In particular, each of the core sheets 11 before lamination might bedifficult to handle since the rigidity of the core sheet 11 is reduced.For example, the rigidity of the core sheet 11 is reduced in a casewhere each first preformed inclined accommodating slot 61 communicateswith the associated second preformed inclined accommodating slot 62.This is because the inner ring 11 s of the core sheet 11 is connected tothe outer ring 11 t by only the inner bridges 8 i. However, sinceinter-inclined slot bridges 8 m connect the inner ring 11 s to the outerring 11 t in the present embodiment, the strength of the core sheet 11is increased, and deformation of the core sheet 11 is prevented, whichfacilitates handling.

FIGS. 21 to 23A show an eighth embodiment of the present invention.

The core sheet 11 shown in FIG. 22 includes two first one-sidecommunication slots 11 e and two independent slots 11 c. These firstone-side communication slots 11 e and the independent slots 11 c are thepreformed radial accommodating slots the number of which is four, thatis, P/2. Each of the first one-side communication slots 11 ecommunicates with the associated first preformed inclined accommodatingslot 61, but does not communicate with the second preformed inclinedaccommodating slot 62. That is, the inner bridge 8 i is formed betweeneach first one-side communication slot 11 e and the associated secondpreformed inclined accommodating slot 62. In FIG. 21, the first one-sidecommunication slots 11 e are located at intervals of 180°. That is, theindependent slots 11 c are also located at intervals of 180°.

The rotor core 8 shown in FIGS. 21 and 23 is manufactured by laminatingthe core sheets 11 of FIG. 22 on the rotor axis 13 while rotating themby 90° one at a time.

The eighth embodiment has the following advantage.

(26) The first one-side communication slots 11 e are arranged at leastat some parts of each radial accommodating slot 8 a along the axialdirection. Thus, gaps are formed between parts of each radialaccommodating slot 8 a corresponding to the first one-side communicationslots 11 e and the radially inner end of the associated first inclinedmagnet 71. Thus, the magnetic resistance is increased, and the magneticflux leakage is reduced. Forming the first one-side communication slots11 e by punching the core sheet 11 is easier than, for example, to formthe inner restricting portions 8 e of FIG. 1. Also, since the innerbridges 8 i connect the inner ring 11 s to the outer ring lit in theradial direction, the strength of each core sheet 11 is increased. Byreducing the thickness of the inner bridges 8 i, the length of the firstinclined magnets 71 and the second inclined magnets 72 is increased.

Also, the embodiment is not limited to laminating the core sheets 11 ofFIG. 22 on the rotor axis 13 while rotating the core sheets 11 one at atime, but the core sheets 11 of FIG. 22 may be laminated while rotatingthe core sheets 11 by 90° one at a time, and witch each core sheet 11being turned over relative to the preceding core sheet 11. In this case,the cross-sectional areas of the inner bridges 8 i on bothcircumferential sides of the radial accommodating slots 8 a are evenalong the entire axial direction of the rotor core 8.

FIGS. 24 to 26A show a ninth embodiment.

As shown in FIG. 25, each core sheet 11 includes two first one-sidecommunication slots 11 e and two second one-side communication slots 11f. That is, the total of four preformed radial accommodating slots ofthe core sheet 11 are all one-side communication slots. The secondone-side communication slots 11 f do not communicate with the firstpreformed inclined accommodating slots 61, and communicate with thesecond preformed inclined accommodating slots 62.

The rotor core 8 of FIGS. 24 and 26 is formed by laminating the coresheets 11 of FIG. 25 on the rotor axis 13 while rotating them by 90° oneat a time.

The ninth embodiment has the following advantages.

(27) Each of the radial accommodating slots 8 a is provided with thefirst one-side communication slots 11 e and the second one-sidecommunication slots 11 f. As a result, the inner bridges 8 i restrictthe first inclined magnets 71 and the second inclined magnets 72 frommoving radially inward.

(28) All the preformed radial accommodating slots are either the firstone-side communication slot 11 e or the second one-side communicationslot 11 f. Thus, for example, as compared to a case where some of thepreformed radial accommodating slots are the independent slots 11 c, themagnetic resistance of the rotor core 8 is increased, thereby reducingthe magnetic flux leakage.

The radial dimension of each of the both-side communication slots 11 d,the independent slot 11 c, the first one-side communication slots 11 e,and the second one-side communication slots 11 f does not need to beuniform. Some of the preformed radial accommodating slots may be theshort slots 11 a and the rest may be the long slots 11 b. The shortslots 11 a restrict the radial magnets 9 from moving radially inward.

FIGS. 27 to 29A show a tenth embodiment.

The core sheet 11 shown in FIG. 28 includes one short independent slot11 g. The short independent slot 11 g is identical to the independentslot 11 c of FIG. 19 with the radial dimension being reduced. The radialdimension of the short independent slot 11 g is less than the longslots, which are the both-side communication slots 11 d.

The core sheets 11 of FIG. 28 are laminated along the rotor axis 13while being rotated by 90° one at a time. As a result, the rotor core 8shown in FIGS. 27 and 29 is manufactured.

The tenth embodiment has the following advantage.

(29) Short slots, that is, the short independent slots 11 g are arrangedat some parts of each radial accommodating slot 8 a along the axialdirection. The short independent slots 11 g form the inner restrictingportions 8 e. The inner restricting portions 8 e restrict the radialmagnets 9 from moving radially inward. Gaps are provided between theradial magnets 9 and some parts of each radial accommodating slot 8 acorresponding to the long slots, that is, the both-side communicationslots 11 d. Thus, the magnetic resistance of the rotor core 8 isincreased, thereby reducing the magnetic flux leakage.

FIGS. 30 to 32A show an eleventh embodiment.

The core sheet 11 shown in FIG. 31 includes one short independent slot11 g, one independent slot 11 c, and two first one-side communicationslots 11 e. That is, the core sheet 11 of FIG. 31 is identical to thecore sheet 11 of FIG. 22 except that one of the independent slots 11 cof the core sheet 11 of FIG. 22 is replaced with the short independentslot 11 g.

The rotor core 8 of FIGS. 30 and 32 is manufactured by laminating thecore sheets 11 of FIG. 31 along the rotor axis 13 while rotating them by90° one at a time.

Therefore, the eleventh embodiment has the advantages of FIGS. 21 to 23Aand the advantages of FIGS. 27 to 29A.

Also, the core sheets 11 of FIG. 31 may be laminated witch each coresheet 11 being turned over relative the preceding core sheet 11. In thiscase, the cross-sectional areas of the inner bridges 8 i on bothcircumferential sides of each radial accommodating slot 8 a are evenalong the entire axial direction of the rotor core 8.

FIGS. 33 to 35A show a twelfth embodiment.

The core sheet 11 shown in FIG. 34 includes two first one-sidecommunication slots 11 e, one second one-side communication slot 11 f,and one second one-side communication short slot 11 h. That is, the coresheet 11 of FIG. 34 is identical to the core sheet 11 of FIG. 25 exceptthat one of the second one-side communication slots 11 f of the coresheet 11 of FIG. 25 is replaced with the short slot, which is the secondone-side communication short slot 11 h.

The rotor core 8 of FIGS. 33 and 35 is manufactured by laminating thecore sheets 11 of FIG. 34 along the rotor axis 13 while rotating them by90° one at a time.

Therefore, the twelfth embodiment has both of the advantages of FIGS. 24to 26A and the advantages of FIGS. 27 to 29A.

FIGS. 36 to 38A show a thirteenth embodiment.

The core sheet 11 shown in FIG. 37 includes one projecting communicationslot 11 j and three both-side communication slots 11 d. That is, thecore sheet 11 of FIG. 37 is identical to the core sheet 11 of FIG. 19except that one independent slot 11 c of the core sheet 11 of FIG. 19 isreplaced with the projecting communication slot 11 j. A substantiallytrapezoidal restricting projection 11 i is formed on the radially innerend of the projecting communication slot 11 j. The radially inner end ofthe projecting communication slot 11 j communicates with thecircumferentially adjacent first preformed inclined accommodating slot61 and the second preformed inclined accommodating slot 62. Therestricting projection 11 i restricts each radial magnet 9 from movingradially inward. The inclined surfaces of the trapezoidal shape of therestricting projection 11 i abut against the associated first inclinedmagnet 71 and the second inclined magnet 72 at a position where thefirst inclined magnet 71 and the second inclined magnet 72 do notcontact the radial magnet 9. As a result, the restricting projection 11i restricts the associated first inclined magnet 71 and the secondinclined magnet 72 from moving radially inward. That is, the restrictingprojection 11 i is not in point contact with but in line contact withthe radial magnet 9, the first inclined magnet 71, and the secondinclined magnet 72 as viewed from the axial direction. The width of therestricting projection 11 i is set greater than the width of theprojecting communication slot 11 j.

The rotor core 8 of FIGS. 36 and 38 is manufactured by laminating thecore sheets 11 of FIG. 37 along the rotor axis 13 while rotating them by90° one at a time.

The thirteenth embodiment has the following advantages.

(30) The projecting communication slot 11 j provided with therestricting projection 11 i is arranged at some parts of each radialaccommodating slot 8 a along the axial direction. The restrictingprojections 11 i restrict the associated radial magnet 9, the firstinclined magnet 71, and the second inclined magnet 72 from movingradially inward, and form a gap between the radial magnet 9 and thefirst inclined magnet 71. Furthermore, the restricting projections 11 iform a gap between the second inclined magnet 72 and the radial magnet9. That is, the restricting projections 11 i omit the inner bridges 8 i.Thus, the magnetic resistance of the rotor core 8 is increased, therebyreducing the magnetic flux leakage.

(31) Forming the projecting communication slot 11 j by punching eachcore sheet 11 is easier as compared to, for example, forming smallprojections that restrict radially inward movement of the radial magnets9, the first inclined magnets 71, and the second inclined magnets 72.

(32) The core sheet 11 of FIG. 37 includes one projecting communicationslot 11 j, and the rest of the preformed radial accommodating slots arethe both-side communication slots 11 d. Thus, the magnetic flux leakageis reduced as compared to, for example, a case where the core sheet 11includes two or more projecting communication slots 11 j, or a casewhere each core sheet 11 includes the independent slots 11 c instead ofthe both-side communication slots 11 d.

FIGS. 39 to 42 show a fourteenth embodiment.

As shown in FIG. 40A, the thickness of each core sheet 11 is referred toas a core sheet thickness T. As shown in FIG. 40B, the radial dimensionof each wide slot 8 c is referred to as a wide radial dimension Y. Thewide radial dimension Y is set equal to 4T (Y=4T) so as to satisfy Y≦4T.In the present embodiment, the core sheet thickness T is set equal to0.4 mm, and the wide radial dimension Y is set equal to 1.6 mm.

As shown in FIG. 40B, the circumferential spacing between each pair ofouter circumferential projections 8 d is referred to as a constrictionspacing XC of each radial accommodating slot 8 a.

As shown in FIG. 40B, the radial dimension of each wide outer bridge 8 kis referred to an outer bridge dimension AB. The radial dimension of theouter circumferential projections 8 d is referred to as a projectionradial dimension W.

As shown in FIG. 40C, the radial dimension of each V-slot outer bridge 8w is also set equal to the outer bridge dimension AB. In the presentembodiment, the outer bridge dimension AB is set to 0.4 mm. That is, theouter bridge dimension AB is set equal to the core sheet thickness T(AB=T).

The circumferential dimension of each inter-inclined slot bridge 8 m isreferred to as an inter-inclined slot bridge dimension BB. Theinter-inclined slot bridge dimension BB is set greater than the outerbridge dimension AB (BB>AB). In the present embodiment, theinter-inclined slot bridge dimension BB is set to 0.6 mm.

As shown in FIG. 40D, the width of the inner bridges 8 i is referred toas an inner bridge dimension CB. The inter-inclined slot bridgedimension BB is set greater than the inner bridge dimension CB (BB>CB).In the present embodiment, the inner bridge dimension CB is set equal to0.4 mm (AB=CB=T).

The fourteenth embodiment has the following advantage.

(33) The wide slots 8 c increase the magnetic resistance at the radiallyouter ends of the radial accommodating slots 8 a, and separate themagnetic paths from the radial magnets 9, thereby reducing the magneticflux leakage of the rotor core 8.

Based on the experimental result of FIG. 41, setting is performed tosatisfy Y≦4T (Y≦1.6 mm). Thus, the strength of the outer circumferentialprojections 8 d is achieved without excessively increasing the wideradial dimension Y of the wide slots 8 c. This achieves the strength ofthe outer circumferential projections 8 d necessary to restrict theradial magnets 9 from moving radially outward. That is, the size of therotor 2 is reduced without reducing the projection radial dimension W ofthe outer circumferential projections 8 d more than necessary. The wideslots 8 c efficiently reduce the magnetic flux leakage, and the size ofthe rotor 2 is reduced.

FIG. 41 shows the experimental result of the relationship betweenchanges in the wide radial dimension Y and the size ratio of the rotor 2necessary to obtain the torque property of a predetermined value. In theexperiment, the diameter of the rotor 2, that is, the diameter of therotor core 8 was fixed, the outer bridge dimension AB was fixed, and thesize of the radial magnets 9 and the radial position of the radialmagnets 9 were fixed. That is, the size ratio of the rotor representsthe axial dimension ratio of the rotor 2, that is, the axial dimensionratio of the rotor core 8. The predetermined value of the torqueproperty was set to the torque property of the rotor core 8 when thewide slots 8 c were not provided. The rotor size ratio required toobtain the predetermined value of the torque property was measured foreach of the cases where the constriction spacing XC was set equal to 0.4mm, 0.8 mm, 1.6 mm, and 2.4 mm. As is mentioned in the description ofthe fourteenth embodiment, AB=T=CB=0.4 mm.

As shown in FIG. 41, as the constriction spacing XC is increased, thesize of the rotor 2 was reduced. This is because as the constrictionspacing XC was increased, the magnetic flux leakage of the rotor core 8was reduced. According to FIG. 41, in the cases of any constrictionspacing XC, the size of the rotor 2 is reduced until the wide radialdimension Y reaches 4T (1.6 mm) from zero. However, even if the wideradial dimension Y is set greater than 4T, the size of the rotor 2cannot be made smaller than the case where Y is equal to 4T (Y=4T).

Thus, according to FIG. 41, when the wide radial dimension Y is setgreater than 4T, the strength of the rotor core 8 is unnecessarilyreduced. This also causes the need for reducing the projection radialdimension W of the outer circumferential projections 8 d, which mightreduce the strength of the outer circumferential projections 8 d.

However, in the present embodiment, Y is set less than or equal to 4T(Y≦4T). Thus, the size of the rotor 2 is reduced without unnecessarilyreducing the strength of the outer circumferential projections 8 d. Forexample, when the strength of the outer circumferential projections 8 dis low, the radial magnets 9 might damage the outer circumferentialprojections 8 d by the centrifugal force caused by rotation of the rotor2. That is, the radial magnets 9 might move radially outward.

However, the present embodiment achieves the strength of the outercircumferential projections 8 d. As a result, the size of the rotor 2 isreduced while preventing the displacement of the radial magnets 9. Thatis, the present embodiment finely optimizes the shape and dimension ofthe wide slots 8 c. The present embodiment provides the dimension of thewide slots 8 c for effectively reducing the magnetic flux leakage. As aresult, the size of the motor is reduced.

(34) Setting is performed to satisfy Y=4T (Y=1.6 mm). Thus, the size ofthe rotor 2 is minimized without unnecessarily reducing the strength ofthe outer circumferential projections 8 d (see FIG. 41).

(35) The outer bridge dimension AB and the inter-inclined slot bridgedimension BB are set to satisfy BB>AB. As apparent from the experimentalresult of FIG. 42, the present embodiment reduces the magnetic fluxleakage as in the case where BB is set equal to AB (BB=AB), and the sizeof the rotor 2 is reduced. The present embodiment achieves the strengthof the inter-inclined slot bridges 8 m, and achieves the strength of therotor core 8 as compared to, for example, the case where BB is set equalto AB (BB=AB).

FIG. 42 shows the experimental result of the size ratio of the rotor 2required to obtain the torque property of the predetermined value whenthe outer bridge dimension AB, the inter-inclined slot bridge dimensionBB, and the inner bridge dimension CB are varied. As a reference value,the rotor size ratio in the case where AB=BB=CB=0.4 mm is referred to asone (the rotor size ratio=1). The rotor size ratio was obtained bysetting each of the outer bridge dimension AB, the inter-inclined slotbridge dimension BB, and the inner bridge dimension CB to 0.6 mm. Whenonly the outer bridge dimension AB was 0.6 mm, the rotor size ratio wasapproximately 1.09. When only the inter-inclined slot bridge dimensionBB was 0.6 mm, the rotor size ratio was approximately 1.06. When onlythe inner bridge dimension CB was 0.6 mm, the rotor size ratio wasapproximately 1.00.

As shown in FIG. 42, the rotor size ratio obtained when BB is equal to0.6 mm is almost equal to 1.00. That is, even if the inter-inclined slotbridge dimension BB is set greater than the outer bridge dimension AB(BB>AB), the rotor size ratio does not change much from the case when BBis equal to AB when the inner bridge dimension CB is fixed. Thus, whenBB is greater than AB (BB>AB), the size of the rotor 2 is reduced as inthe case where BB is equal to AB (BB=AB). That is, when BB is greaterthan AB (BB>AB), the strength of the inter-inclined slot bridges 8 m isachieved as compared to the case where BB is equal to AB (BB=AB). Thatis, by setting the inter-inclined slot bridge dimension BB to be greaterthan the outer bridge dimension AB, the strength of the rotor core 8 isincreased while maintaining the torque property.

(36) The inner bridge dimension CB and the inter-inclined slot bridgedimension BB are set such that BB is greater than CB (BB>CB). Asapparent from FIG. 42, the magnetic flux leakage is reduced, and thesize of the rotor 2 is reduced as in the case when BB is equal to CB(BB=CB). Furthermore, when BB is greater than CB (BB>CB), the strengthof the inter-inclined slot bridges 8 m is increased than the case whenBB is equal to CB (BB=CB).

As shown in FIG. 42, when the outer bridge dimension AB is fixed, evenif the inter-inclined slot bridge dimension BB is set to 0.6 mm, whichis greater than the inner bridge dimension CB, the rotor size ratio doesnot become greater than the case where BB=CB=0.4 mm. Thus, by settingthe inter-inclined slot bridge dimension BB to be greater than the innerbridge dimension CB, the size of the rotor 2 is reduced as in the casewhere BB is equal to CB (BB=CB). Furthermore, the strength of theinter-inclined slot bridges 8 m is increased, thus increasing thestrength of the rotor core 8.

(37) The outer bridge dimension AB is set equal to T (AB=T). Thus, thecross-section of the wide outer bridge 8 k and the V-slot outer bridge 8w in each core sheet 11 is square. Thus, the present embodimentincreases the strength of the wide outer bridges 8 k and the V-slotouter bridges 8 w while reducing the magnetic flux leakage of the wideouter bridges 8 k and the V-slot outer bridges 8 w as compared to, forexample, a case where AB is not equal to T.

FIGS. 43 to 48 show a fifteenth embodiment.

As shown in FIG. 43, the embedded magnet motor includes a motor case 41,which accommodates the stator 1. The motor case 41 includes a yoke 42and an end plate 43. The yoke 42 is a cylinder having a bottom. The endplate 43 closes the opening of the yoke 42. The stator 1 is secured tothe inner circumferential surface of the yoke 42.

A first bearing 33 is arranged at the bottom portion of the yoke 42. Asecond bearing 34 is arranged at the center of the end plate 43. Thefirst bearing 33 and the second bearing 34 rotatably support therotating shaft 7.

As shown in FIG. 43, a Hall IC 51 is arranged on the end plate 43 via asubstrate 52. The Hall IC 51 is a magnetic sensor, which detectsrotation of the rotor 2 by detecting the magnetic flux leakage of therotor 2 in the axial direction. That is, the Hall IC 51 detects therotation position of the rotor 2, that is, the rotational angle. TheHall IC 51 faces an axial end surface 2 a of the rotor 2. Based onsignals from the Hall IC 51, a controller (not shown) generates optimalrotating magnetic field from the stator 1, and as a result, reliablyrotates the rotor 2.

As shown in FIGS. 44 and 45, the Hall IC 51 is arranged radially outwardthan the fastening slot 18 located between one of the first inclinedmagnets 71 and the associated second inclined magnet 72. The Hall IC 51is arranged in a radially outer region H of the rotor core 8. Thepositive and negative poles of the magnetic flux detected in theradially outer region H are reversed only once per cycle of rotation ofthe rotor 2.

The side surfaces of the first inclined magnet 71 and the secondinclined magnet 72 facing each other are referred to as inclined magnetsurfaces 71 a, 72 a. As viewed from the axial direction, the centers ofthe inclined magnet surfaces 71 a, 72 a are referred to as center pointsMX. In the present embodiment, the radially outer region H is locatedradially outward than the center points MX. That is, the radially outerregion H is a region between the center points MX and the rotor outercircumferential surface 8 r.

The radially outer region H refers to a region of the rotor core 8between each first inclined magnet 71 and the associated second inclinedmagnet 72 where the magnetic flux density is high when electric power isnot supplied to the coils 6. That is, the radially outer region H is ahigh magnetic flux density region of the rotor core 8 when electricpower is not supplied to the motor. The radially outer region Hcorresponds to a region of the rotor core 8 that reaches magneticsaturation (based on an experimental result, which is not shown). Thatis, the radially outer region H is a magnetic saturation region of therotor core 8.

FIGS. 46 to 48 explain a designing method of the embedded magnet motorfor determining the radial position of the Hall IC 51. The designingmethod includes a measuring step S1 and a positioning step S2. That is,the designing method is a manufacturing method of the embedded magnetmotor.

First, in the measuring step S1, the position of the Hall IC 51 isdetermined to face the axial end surface 2 a of the rotor 2.Furthermore, while changing the radial position of the Hall IC 51, themagnetic flux characteristics of each radial position is measured. Asshown in FIG. 46, the positions of a first Hall IC 51 a to an eighthHall IC 51 h are set from an inner circumferential surface 8 v of therotor 2 to the rotor outer circumferential surface 8 r. FIG. 47 shows afirst magnetic flux density characteristic Za to a fifth magnetic fluxdensity characteristic Ze of the first Hall IC 51 a to the fifth Hall IC51 e in relation to the rotational angle of the rotor core 8. FIG. 48shows a sixth magnetic flux density characteristic Zf to an eighthmagnetic flux density characteristic Zh of the sixth Hall IC 51 f to theeighth Hall IC 51 h.

As shown in FIG. 47, the first magnetic flux density characteristic Zato the fifth magnetic flux density characteristic Ze pass a point wherethe magnetic flux density is equal to zero several times during onecycle of the magnetic flux variation. That is, several zero crossingsoccur during one cycle of the magnetic flux variation. That is, thepositive and negative signs of the magnetic flux density are reversedseveral times. The reversion of the positive and negative poles of themagnetic flux is detected at each of the north pole and the south poleof the rotor 2. One cycle of the magnetic flux variation is a periodduring which the rotor 2 is rotated by 90°, that is, a period duringwhich the pair of the first inclined magnet 71 and the second inclinedmagnet 72 pass the Hall IC 51. That is, one cycle of the magnetic fluxvariation is a period between the pair of first inclined magnet 71 andthe second inclined magnet 72. For example, the fourth magnetic fluxdensity characteristic Zd is increased from zero (the magnetic fluxdensity=0) to approximately 130 mT, and then reduced to approximately−30 mT. Then, after being increased to approximately 30 mT, the fourthmagnetic flux density characteristic Zd is reduced to approximately −150mT, and then becomes zero (magnetic flux density=0). That is, the fourthmagnetic flux density characteristic Zd cause three zero crossingsduring one cycle.

As shown in FIG. 48, the sixth magnetic flux density characteristic Zfto the eighth magnetic flux density characteristic Zh pass a point wherethe magnetic flux density is equal to zero only once during one cycle ofthe magnetic flux variation. That is, zero crossing occurs only once.That is, the positive and negative poles of the magnetic flux detectedbetween the first inclined magnet 71 and the second inclined magnet 72is reversed only once during one cycle.

In the position determining step S2, the radially outer region H isspecified, and the position of the Hall IC 51 is determined in theradially outer region H based on the result of the measuring step S1.The sixth magnetic flux density characteristic Zf to the eighth magneticflux density characteristic Zh, in which the positive and negative polesof the magnetic flux are reversed only once during one cycle of themagnetic flux variation, are specified as shown in FIG. 48. As a result,the radial positions of the sixth Hall IC 51 f to the eighth Hall IC 51h shown in FIG. 46 are specified as the radially outer region H.

As shown in FIG. 45, in the present embodiment, the Hall IC 51 isarranged at the position of the seventh Hall IC 51 g corresponding tothe seventh magnetic flux density characteristic Zg. As shown in FIG.46, a line that connects points on the first inclined magnet 71 and thesecond inclined magnet 72 that are the closest to each other is referredto as a narrowest line L. The seventh Hall IC 51 g is locatedimmediately radially inward of the narrowest line L.

As shown in FIG. 45, the fastening slot 18 and the rivet 19 are arrangedto be adjacent to and radially inward of the radially outer region H. InFIG. 45, a middle circle MC, which is a circle that passes through thecenter point MX of the first inclined magnet 71 and the center point MXof the second inclined magnet 72, is shown by a chain-double dashed linearound the rotor axis 13. The fastening slot 18 is arranged radiallyinward of the middle circle MC. The distance between the seventh Hall IC51 g and the fastening slot 18 is greater than the size of the sixthHall IC 51 f.

The fifteenth embodiment has the following advantage.

(38) The Hall IC 51 is arranged to face the axial end surface 2 a of therotor 2. The Hall IC 51 is arranged in the radially outer region H. Thepositive and negative poles of the magnetic flux detected by the Hall IC51 are reversed only once during one cycle of the magnetic fluxvariation between the first inclined magnet 71 and the second inclinedmagnet 72 in the radially outer region H. That is, the detected magneticflux density undergoes zero crossing only once during one cycle of themagnetic flux variation. Thus, the present embodiment detects therotation position of the rotor 2 highly accurately with a simplestructure without using a resolver or a sensor magnet.

That is, the present embodiment eliminates the necessity of an expensiveresolver that has a complicated structure. Also, the present embodimentuses the magnetic flux of the radial magnets 9, the first inclinedmagnets 71, and the second inclined magnets 72, which configure themagnetic poles of the rotor 2. Thus, an additional sensor magnet is notused. Therefore, the present embodiment reduces the number of componentsand the size, and has a simple structure. That is, the presentembodiment does not require a sensor rotor of a resolver, and it is alsonot necessary to determine the position of the sensor magnet on therotor with high accuracy.

As shown in FIG. 46, the first Hall IC 51 a to the fifth Hall IC 51 eare arranged radially inward than the radially outer region H. In thiscase, if the positive and negative poles of the detected magnetic fluxof the Hall IC 51 are reversed twice or more between the first inclinedmagnet 71 and the second inclined magnet 72, the pole of the detectedmagnetic flux is reversed also at points other than the turning point ofthe magnetic poles of the rotor 2 like the first magnetic flux densitycharacteristic Za to the fifth magnetic flux density characteristic Zeshown in FIG. 47. That is, in the case of FIG. 47, detection of therotation position of the rotor 2 is difficult. However, the presentembodiment shown in FIG. 48 avoids such a problem. That is, the presentembodiment easily and highly accurately detects the rotation position ofthe rotor 2 with a simple structure. Thus, the rotating magnetic fieldoptimal for the stator 1 is generated, and the rotation and drive of therotor 2 is reliably controlled.

As a comparative example, the rotation position of the rotor may bedetected with high accuracy using, for example, a resolver. However, theresolver has a complicated structure and is expensive. Furthermore, whenusing the resolver, the circumferential position of a sensor rotor,which is rotated integrally with the rotor, needs to be determined withhigh accuracy to detect the rotation position (angle) of the rotor withhigh accuracy. Also, when using a sensor magnet, which rotatesintegrally with the rotor, and a magnetic sensor, which detects themagnetic flux of the sensor magnet, instead of the resolver, highaccuracy is required to determine the position of the sensor magnet inthe circumferential direction of the rotor. That is, the same problem asthe resolver arises when using the sensor magnet in addition to thefirst inclined magnets 71 and the second inclined magnets 72. In thepresent embodiment, the resolver and the additional sensor magnet areunnecessary since the magnetic flux of the first inclined magnets 71 andthe second inclined magnets 72 is measured by arranging the Hall IC 51in the radially outer region H.

(39) The radially outer region H is a region in the rotor core 8 wherethe magnetic flux density is high when electric power is not supplied tothe embedded magnet motor. That is, the radially outer region H is themagnetic saturation region of the rotor core 8. The fastening slots 18and the rivets 19 are arranged adjacent to and radially inward of theradially outer region H.

For example, when arranging the fastening slots 18 and the rivets 19 inthe magnetic saturation region, the cogging torque and the torque ripplemight be adversely affected. However, since the fastening slots 18 andthe rivets 19 of the present embodiment are arranged outside theradially outer region H, the adverse affect is avoided. Furthermore, thefastening slots 18 and the rivets 19 are arranged adjacent to theradially inner end of the radially outer region H. Thus, the fasteningslots 18 and the rivets 19 are arranged radially outward as much aspossible, which maximizes the mechanical strength of the rotor core 8.

(40) The designing method of the embedded magnet motor, that is, themanufacturing method includes the measuring step S1 and the positiondetermining step S2. In the measuring step S1, the Hall IC 51 fordetecting rotation, which detects the magnetic flux leakage of the rotor2 in the axial direction, is arranged to face the axial end surface 2 aof the rotor 2. In the measuring step S1, while changing the radialposition of the Hall IC 51, the magnetic characteristic of the rotor 2for each radial position is measured. In the position determining stepS2, the radially outer region H is determined based on the result of themeasuring step S1, and the position of the Hall IC 51 is determined inthe radially outer region H. The positive and negative poles of themagnetic flux detected by the magnetic sensor arranged in the radiallyouter region H are reversed only once during one cycle of the magneticflux. Thus, the embedded magnet motor of the present embodiment iseasily designed and manufactured.

The above embodiments may be modified as follows.

In FIG. 2, the number of the short slot 11 a of each core sheet 11 doesnot need to be one, but may be two or more. The number of the long slots11 b of each core sheet 11 is obtained by subtracting the number of theshort slots 11 a from (P/2).

The short slots 11 a are preferably arranged at regular intervals alongthe axial direction of the rotor core 8. That is, the inner restrictingportions 8 e are preferably distributed at regular intervals in theaxial direction of the radial accommodating slots 8 a. Each of the coresheets 11 may include two short slots 11 a arranged next to each otherin the circumferential direction, and two long slots 11 b arranged nextto each other in the circumferential direction. In this case, severalcore sheets are laminated while being rotated by 180° each. Also,several core sheets 11 may be laminated with each core sheet 11 beingturned over relative to the preceding core sheet 11. In these cases, theshort slots 11 a, that is, the inner restricting portions 8 e aredistributed at regular intervals in the axial direction of the radialaccommodating slots 8 a.

The short slots 11 a, that is, the inner restricting portions 8 e may bearranged at uneven intervals in the axial direction of the radialaccommodating slots 8 a.

The second radial distance R2 does not need to be less than or equal tothe third radial distance R3, but may be set greater than the thirdradial distance R3.

The first radial distance R1 does not need to be greater than the thirdradial distance R3, but may be set less than or equal to the thirdradial distance R3.

In FIG. 1A, the overlap dimension R does not need to be set to SW/2, butmay be set to satisfy 0<R≦SW/4. According to the experimental result ofFIG. 4, when 0<R≦SW/4 is satisfied, the magnetizing rate issubstantially the maximum. Thus, inefficiency of the radial magnets 9 isfurther reduced.

In FIG. 2, the outer circumferential projections 8 d do not need to beformed only in the short slot 11 a of each core sheet 11, but may beformed in the long slots 11 b. The outer circumferential projections 8 dmay be formed in all the preformed radial accommodating slots. That is,in FIG. 3, the outer circumferential projections 8 d do not need to bearranged at some parts of each radial accommodating slot 8 a along theaxial direction, but may be arranged over the entire axial direction ofeach radial accommodating slot 8 a.

In FIG. 8, the inward projections 8 n do not need to be formed at onlysome parts of each radial accommodating slot 8 a along the axialdirection, but may be formed over the entire axial direction of eachradial accommodating slot 8 a.

In the core sheet 11 of FIG. 6, the inward projection 8 n does not needto be arranged only in the short slot 11 a, but may be arranged also inthe long slots 11 b.

The third width W3 of the inward projections 8 n of FIG. 7 does not needto be set approximately ⅓ of the first width W1 of the radial magnets 9.The third width W3 of the inward projections 8 n of FIG. 7 may take anyvalue as long as it is less than the first width W1 of the radialmagnets 9. To suppress the magnetic flux leakage via the inwardprojections 8 n, the third width W3 of the inward projections 8 n ispreferably set less than or equal to ½ the first width W1 of the radialmagnets 9.

In FIG. 12, the inner circumferential projection 8 u does not need to bearranged only on the radial accommodating slot side surface 8 p of theradial accommodating slot 8 a that is in the counterclockwise direction,but may be arranged on the radial accommodating slot side surface 8 pthat is in the clockwise direction.

In FIG. 12, the number of the inner circumferential projection 8 uformed in each core sheet 11 is not limited to one, but may be two ormore. The inner circumferential projections 8 u are preferably arrangedat regular intervals in the axial direction of the rotor core 8. Also,when forming the inner circumferential projections 8 u in the twopreformed radial accommodating slots arranged next to each other in thecircumferential direction, the core sheets 11 may be laminated whilebeing rotated by 180° each, or the core sheets 11 may be laminated witheach core sheet 11 being turned over relative to the preceding coresheet 11. In these cases, the inner circumferential projections 8 u arelocated at regular intervals in the axial direction of the rotor core 8.

In FIG. 13, the inner circumferential projections 8 u may be arranged atuneven intervals in the axial direction of the rotor core 8.

In FIG. 19, the number of the independent slot 11 c formed in each coresheet 11 is not limited to one, but may be two or more. The number ofthe both-side communication slots 11 d of each of the core sheet 11 isobtained by subtracting the number of the independent slots 11 c from(P/2). The independent slots 11 c are preferably arranged at regularintervals in the axial direction of the rotor core 8. This is becausethe inner bridges 8 i will be arranged at regular intervals in the axialdirection of the rotor core 8.

In the core sheet 11 of FIG. 19, two independent slots 11 c may bearranged next to each other in the circumferential direction, and twoboth-side communication slots 11 d may be arranged next to each other inthe circumferential direction. The circumferential intervals between theindependent slots 11 c and between the both-side communication slots 11d are 90°. In this case, the core sheets 11 may be laminated while beingrotate by 180° each, or the core sheets 11 may be laminated with eachcore sheet 11 being turned over relative to the preceding core sheet 11.In these cases, the independent slots 11 c are arranged at regularintervals in the axial direction of the rotor core 8.

The independent slots 11 c and the inner bridges 8 i may be arranged atuneven intervals in the axial direction of the rotor core 8.

In the core sheet 11 of FIG. 19, the preformed radial accommodatingslots do not need to be either the independent slots 11 c or theboth-side communication slots 11 d. The preformed radial accommodatingslots may be anything as long as the inner bridges 8 i are formed atsome parts of the rotor core 8 along the axial direction.

The core sheets 11 of FIG. 22 may be laminated such that the firstone-side communication slots 11 e are arranged at least at some parts ofeach radial accommodating slot 8 a along the axial direction.

In FIG. 40B, the wide radial dimension Y of the wide slots 8 c and thecore sheet thickness T do not need to be set to satisfy Y=4T, but may beset to satisfy Y<4T. For example, Y may be set equal to 2T, that is, 0.8mm.

In FIGS. 40B to 40D, the outer bridge dimension AB, the inter-inclinedslot bridge dimension BB, and the inner bridge dimension CB do not needto be set to BB=0.6 mm and AB=CB=0.4 mm. That is, setting does not needto be performed to satisfy BB>AB=CB. For example, the outer bridgedimension AB, the inter-inclined slot bridge dimension BB, and the innerbridge dimension CB may be set to AB=BB=CB, that is, 0.4 mm. That is,when the outer bridge dimension AB differs from the inner bridgedimension CB, the size of the rotor 2 is increased corresponding to thegreater value as apparent from FIG. 42. Thus, it is preferable to set ABequal to BB.

In FIGS. 39 and 44, the wide slots 8 c and the outer circumferentialprojections 8 d do not need to be formed along the entire axialdirection of the rotor core 8, but may be formed at some parts of therotor core 8 along the axial direction. For example, the wide slots 8 cand the outer circumferential projections 8 d may be formed at bothaxial ends of the rotor core 8, or in every tenth core sheets 11. Alsoin FIG. 44, the wide slots 8 c may be eliminated. The radial magnets 9may be extended to the radially outer end of the radial accommodatingslots.

In FIG. 39, the pair of outer circumferential projections 8 d projectfrom the circumferential ends of each radial accommodating slot 8 a bythe same projection amount. However, the outer circumferentialprojections 8 d may project from only one circumferential side of eachradial accommodating slot 8 a. Also, the pair of outer circumferentialprojections 8 d may project from both circumferential sides by differentprojection amounts.

In FIG. 46, the Hall IC 51 is not limited to be arranged as the seventhHall IC 51 g, but may be changed to the sixth Hall IC 51 f or the eighthHall IC 51 h. The sixth Hall IC 51 f is adjacent to and radially outwardof the middle circle MC. That is, the sixth Hall IC 51 f is locatedimmediately radially outward of one of the fastening slots 18 and theassociated rivet 19. The distance between the sixth Hall IC 51 f and thenarrowest line L is greater than the size of the seventh Hall IC 51 g.The eighth Hall IC 51 h is adjacent to and radially outward of thenarrowest line L.

As shown in FIG. 48, among the sixth magnetic flux densitycharacteristic Zf to the eighth magnetic flux density characteristic Zh,the one that has the steepest inclination around the point where themagnetic flux density becomes zero is the eighth magnetic flux densitycharacteristic Zh. That is, the eighth Hall IC 51 h accuratelydiscriminates the changes in the magnetic poles, and is most suitablefor detecting the rotation position of the rotor 2. The eighth Hall IC51 h is arranged most radially outward in the rotor 2. Thus, the eighthmagnetic flux density characteristic Zh has a greater inclination thanthe sixth magnetic flux density characteristic Zf and the seventhmagnetic flux density characteristic Zg around the point where thepositive and negative poles of the magnetic flux are reversed.

In FIG. 45, the fastening slots 18 and the rivets 19 do not need to bearranged adjacent to and radially inward of the radially outer region H.The rivet 19 may be changed to other tightening member such as a boltand a nut. The rotor core 8 does not need to be manufactured bylaminating the core sheets 11. For example, the rotor core 8 may bemanufactured by sintering magnetic powder. That is, the rotor core 8 maybe a sintered core, and the sintered core eliminates the need for thefastening slots 18 and the rivets 19.

The measuring step S1 is not limited to measuring the first magneticflux density characteristic Za to the eighth magnetic flux densitycharacteristic Zh of the first Hall IC 51 a to the eighth Hall IC 51 h.The radially outer region H may be determined based on the center pointsMX of each first inclined magnet 71 and the associated second inclinedmagnet 72.

In FIG. 1, the V-slot outer gaps 8 g do not need to be formed. Theradially outer ends of the first inclined accommodating slots 81 maycontact the first inclined magnets 71. Also, the radially outer ends ofthe second inclined accommodating slots 82 may contact the secondinclined magnets 72.

In FIG. 1, each pair of the first inclined accommodating slot 81 and thesecond inclined accommodating slot 82 do not need to be disconnectedfrom each other, but may communicate with each other. That is, each pairof the first inclined accommodating slot 81 and the second inclinedaccommodating slot 82 do not need to be independent from each other, butmay communicate with each other at the radially outer end of theV-shaped accommodating slot 8 b to form one slot.

In FIG. 1A, the width of the inner bridges 8 i does not need to beconstant along the radial direction, but may change along the radialdirection. For example, in FIG. 1A, the triangular gaps 8 j may beomitted.

The core sheets 11 of FIG. 2 do not need to be laminated around therotor axis 13 while being rotated one at a time so that each of the coresheets 11 is displaced in the circumferential direction. The core sheets11 may be laminated while rotating every set of core sheets 11 of acertain number. In this case, the number of times the core sheets 11 arerotated is reduced, which facilitates the manufacture.

The core sheets 11 forming the rotor core 8 do not need to be one type,but several types of core sheets may be used. For example, the number ofthe short slots 11 a of each core sheet 11 may differ from one another.

In FIG. 1, the first inclined magnets 71 and the second inclined magnets72 do not need to be substantially rectangular solid, but may be curvedto form an arcuate shape, or the width may be irregular.

That is, in the V-shaped accommodating slots 8 b, the straight linesthat form the V-shape may be curved, or the width of the straight linesof the V-shaped accommodating slots 8 b may be irregular.

The radial magnets 9, the first inclined magnets 71, the second inclinedmagnets 72, and the rotor core 8 of FIG. 1 do not need to be one bodyextending over the entire axial direction of the rotor core 8. Theradial magnets 9, the first inclined magnets 71, the second inclinedmagnets 72, and the rotor core 8 may be divided in the axial direction.The divided members may be displaced in the circumferential directionand be laminated in the direction of the rotor axis 13. In this case,the cogging torque and the torque ripple of the embedded magnet motorare further reduced. This is because, rapid magnetic flux change betweenthe stator 1 and the rotor 2 is further reduced.

The number of the teeth 4 and the number of the magnetic poles P of FIG.1 may be changed. That is, the number of the radial magnets 9, the firstinclined magnets 71, and the second inclined magnets 72 may be changedto other than four.

1. An embedded magnet motor comprising a rotor, wherein the rotorincludes a rotor core, a plurality of radial magnets, a plurality offirst inclined magnets and a plurality of second inclined magnets, andwherein each plurality of magnets comprises a number defined by P/2;wherein the rotor core includes a plurality of radial accommodatingslots, a plurality of first inclined accommodating slots and a pluralityof second inclined accommodating slots and wherein each plurality ofslots comprises a number defined by P/2, and wherein the radialaccommodating slots, the first inclined accommodating slots, and thesecond inclined accommodating slots extend entirely through the rotorcore in an axial direction, wherein the radial accommodating slotsextend substantially in a radial direction of the rotor core, and thefirst inclined accommodating slots and the second inclined accommodatingslots extend linearly to be inclined with respect to the radialdirection, wherein each pair of an inclined first accommodating slot andan associated second inclined accommodating slot form a V-shapedaccommodating slot, the V-shape accommodating slot pointing radiallyoutward of the rotor core, the radial accommodating slots and theV-shaped accommodating slots being arranged alternately in acircumferential direction of the rotor core, each of the radialaccommodating slots accommodating one of the radial magnets, each offirst inclined accommodating slots accommodating one of first inclinedmagnets, and each of the second inclined accommodating slotsaccommodating one of the second inclined magnets, wherein each of theradial magnets is located between one of the first inclined magnets andone of the second inclined magnets, wherein each radial magnet and acircumferentially adjacent first inclined magnet form one of a northpole and a south pole, and each radial magnet and a circumferentiallyadjacent second inclined magnet form the other one of the north pole andthe south pole, and as a result, a plurality of north poles and aplurality of south poles are formed and wherein each plurality of polescomprises a number defined by P/2, and wherein P comprises a number ofmagnetic poles of the rotor, wherein a direction perpendicular to thedirection in which each radial accommodating slot extends as viewed fromthe axial direction is referred to as a width direction, and wherein theembedded magnet motor includes a magnetic sensor, and the magneticsensor detects rotation of the rotor by detecting axial magnetic fluxleakage from the rotor, and wherein the magnetic sensor is arranged in aradially outer region to face an axial end surface of the rotor, themagnetic sensor in the radially outer region detects the magnetic flux,and positive and negative poles of the magnetic flux are reversed onlyonce in one cycle of magnetic flux variation during a period when therotor is rotated and the magnetic sensor passes between the firstinclined magnet and the second inclined magnet, wherein the radiallyouter region is a magnetic saturation region of the rotor between one ofthe first inclined magnets and the associated second inclined magnetwhen electricity is not supplied to the embedded magnet motor.
 2. Theembedded magnet motor according to claim 1, wherein the rotor core isformed by laminating a plurality of core sheets in the axial directionand wherein each core sheet includes a fastening slot that extendsthrough the axial direction, the core sheets being secured by afastening member that is inserted within the fastening slot and whereinthe fastening slot and the fastening member are positioned adjacent theradially outer region.
 3. The embedded magnet motor according to claim1, wherein the surfaces of each first inclined magnet and the associatedsecond inclined magnet that face each other are referred to as inclinedmagnet surfaces, and a center of each inclined magnet surface isreferred to as a center point, and wherein the radially outer region islocated radially outward of the center points.